The present invention relates to a method for freeze molding for ceramic powders such as alumina, silicon carbide, and silicon nitride, and metallic powders such as Fe, Cr, and Al.
As methods for molding ceramic or metallic powder materials, there have conventionally been known various kinds of methods such as press molding, slip casting, and injection molding. Freeze molding has also been used mainly when medical and pharmaceutical products, foodstuffs, or the like are molded. In the conventional method for freeze molding, to a material such as a foodstuff are added a dispersion medium such as water and various kinds of molding aids, the material is poured into a molding die having a desired configuration, and the material is maintained in a molding die at a temperature of a freezing point or lower to freeze the material so as to obtain a compact having a desired configuration. The conventional method for freeze molding has advantages in being able to impart a complex configuration to the compact, providing a wide selection of materials for a molding die, and the like.
However, the conventional method for freeze molding has some problems. For example, a compact should be kept at or around a temperature of freezing point. Otherwise, the compact melts and the configuration of the compact cannot be maintained.
Further, when a metallic molding die, a resin molding die, or the like is used in the conventional method for freeze molding and a mixture (material slurry) of a ceramic powder and a dispersion medium is frozen, the surface of the frozen compact adheres to the inner surface of the molding die, thereby deteriorating mold releasability. Accordingly, the frozen compact is released from the molding die by force in this state, and the frozen compact is prone to deform or break.
The present invention is intended to solve the aforementioned problems and provide a method for freeze molding, which gives a compact being able to maintain a desired configuration without melting even if the compact is kept at a temperature over the freezing point, and which enhances mold releasability so as to ease a release of the frozen compact from a molding die and hardly causes a deformation or breakage of the frozen compact when the compact is released.